Hillary Clinton raised objections to fracking for oil and natural gas during the Democratic debate last night, saying the process would be substantially limited if she’s elected.

She would oppose hydraulic fracturing in states that do not want it and apply regulations to reduce methane emissions and protect water, Clinton said, emphasizing past statements.

“I don’t support it when any locality or any state is against, No. 1. I don’t support it when the release of methane or contamination of water is present. I don’t support it, No. 3, unless we can require that anybody who fracks can tell us exactly what chemicals they are using,” Clinton said.

“So by the time we get through all of my conditions, I do not think there will be many places in America where fracking will continue to take place,” she said.

Fracking is a key issue for many environmentalists in part because the wells can release methane, a potent greenhouse gas. The Obama administration has proposed rules to limit methane at new oil and gas wells, and environmental groups are pushing the president to extend the regulations to existing operations.

Vermont Sen. Bernie Sanders used the issue last night to portray himself as the stronger candidate on climate change. The debate was held in Flint, Mich., which is in crisis following the discovery of lead poisoning in the city’s drinking water.

“My answer is a lot shorter. No, I do not support fracking,” Sanders said to loud applause.

“If we don’t get our act together, the planet that we’re going to leave our children may not be healthy and habitable,” he said of global warming. “I have introduced the most comprehensive climate change legislation in the history of the Senate, which among other things calls for a tax on carbon, massive investments in energy efficiency, wind, solar and other sustainable energies. This is a crisis we have got to deal with now.”

Clinton has also proposed a plan to address warming. It focuses on expanding renewable energy and energy efficiency. She has pledged to power every home in the United States with clean energy by the end of her second term. Clinton has not proposed a carbon tax, one of Sanders’ most aggressive climate policies.

“I think I have the most comprehensive plan to combat climate change,” Clinton said last night. “It sets some very big goals.”

Both candidates called for the resignation of Michigan Gov. Rick Snyder (R) for failing to act sooner to mitigate the poisoned water. Environmental advocates claimed that Republican presidential candidates, who debated in the state Thursday, are avoiding the lead crisis and are mostly dismissing climate change.

“While the Democratic candidates proposed serious responses and actual solutions to the Flint water crisis and the climate crisis, the GOP candidates did everything they could to almost entirely ignore both,” said Michael Brune, executive director of the Sierra Club, in a statement.

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